What was once the I-95 landfill near Lorton, Virginia, is now dozens of acres of rolling green fields - dotted by more than 200 metal pipes emerging from the grass.

The pipes are wellheads for natural gas, and they are collecting the methane generated by more than 10 million tons of decomposing garbage dumped by Washington, D.C.-area residents over the course of 30 years.

A vacuum pump draws the gas from underground, through the wellheads, and connects it to roughly 14 miles of pipeline that run throughout the landfill. Under each wellhead, says Mike Malfitano, an environmental technical specialist for Fairfax County, “there’s a three-foot bore hole that goes 110 feet down into the waste mass.”